linux-kernel - Re: [patch] Staging: tidspbridge: make mmap root-only so it is not a security problem

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Date:	Sun, 01 Dec 2013 20:14:37 +0200
From:	Ivajlo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>,
	Pavel Machek <pavel@....cz>
CC:	Pali Rohá <pali.rohar@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Ивайло Д <freemangordon@....bg>,
	sre@...g0.de, omar.ramirez@...itl.com, tony@...mide.com,
	felipe.contreras@...il.com, s-anna@...com, nm@...com,
	ohad@...ery.com, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org, nico@...lde.de
Subject: Re: [patch] Staging: tidspbridge: make mmap root-only so it is not
 a security problem


On 01.12.2013 14:27, Dan Carpenter wrote:
> On Sun, Dec 01, 2013 at 01:10:06PM +0100, Pavel Machek wrote:
>> diff --git a/drivers/staging/tidspbridge/rmgr/drv_interface.c b/drivers/staging/tidspbridge/rmgr/drv_interface.c
>> index 1aa4a3f..a8e86cf 100644
>> --- a/drivers/staging/tidspbridge/rmgr/drv_interface.c
>> +++ b/drivers/staging/tidspbridge/rmgr/drv_interface.c
>> @@ -258,7 +258,17 @@ err:
>>   /* This function maps kernel space memory to user space memory. */
>>   static int bridge_mmap(struct file *filp, struct vm_area_struct *vma)
>>   {
>> -	u32 status;
>> +	int status;
>> +	struct omap_dsp_platform_data *pdata =
>> +	    omap_dspbridge_dev->dev.platform_data;
>> +	unsigned long start = vma->vm_pgoff << PAGE_SHIFT;
>> +		
>> +	if (start < pdata->phys_mempool_base)
>> +		return -EINVAL;
>> +
>> +	if (vma->vm_end - vma->vm_start + (start - pdata->phys_mempool_base)
>> +	    > pdata->phys_mempool_size)
> This test is vulnerable to integer overflows if you pick a very high
> value for start.  Consider using the vm_iomap_memory() helper function
> instead of calling remap_pfn_range() directly.  Commit 7314e613d5ff
> ('Fix a few incorrectly checked [io_]remap_pfn_range() calls') has an
> example of how the conversion works.
>
> regards,
> dan carpenter
>
Dan,

If that one looks fine, I'll send a correctly formatted patch.

Pavel - feel free you to do it, I don't want to "steal" your bug :) .

Patch tested with Maemo5 on n900:

diff --git a/drivers/staging/tidspbridge/rmgr/drv_interface.c 
b/drivers/staging/tidspbridge/rmgr/drv_interface.c
index 1aa4a3f..2d500ea 100644
--- a/drivers/staging/tidspbridge/rmgr/drv_interface.c
+++ b/drivers/staging/tidspbridge/rmgr/drv_interface.c
@@ -258,8 +258,9 @@ err:
  /* This function maps kernel space memory to user space memory. */
  static int bridge_mmap(struct file *filp, struct vm_area_struct *vma)
  {
-    u32 status;
-
+    struct omap_dsp_platform_data *pdata =
+        omap_dspbridge_dev->dev.platform_data;
+
      /* VM_IO | VM_DONTEXPAND | VM_DONTDUMP are set by remap_pfn_range() */
      vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

@@ -268,13 +269,9 @@ static int bridge_mmap(struct file *filp, struct 
vm_area_struct *vma)
          vma->vm_start, vma->vm_end, vma->vm_page_prot,
          vma->vm_flags);

-    status = remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
-                 vma->vm_end - vma->vm_start,
-                 vma->vm_page_prot);
-    if (status != 0)
-        status = -EAGAIN;
-
-    return status;
+    return vm_iomap_memory(vma,
+                   pdata->phys_mempool_base,
+                   pdata->phys_mempool_size);
  }

  static const struct file_operations bridge_fops = {





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